 public ListNode FindKthToTail (ListNode pHead, int k) {
        // write code here
        if(pHead == null || k == 0){
            return null;
        }
         
        ListNode fast = pHead;
        ListNode slow = pHead;
        for(int i = 0; i < k-1; i++){
            fast = fast.next;
            if(fast == null){
                return null;
            }
        }
         
        while(fast.next != null){
            fast = fast.next;
            slow = slow.next;
        }
        return slow;
 
         
    }